Posterior Palatal Seal

Presented by-Dr.Shrey Suri1st year PG

INTRODUCTIONThe diagnostic evaluation and placement of the

posterior palatal seal is of great importance.

The posterior border of maxillary denture has definite anatomic and physiologic boundaries ,once understood, make the placement of the placement of posterior palatal seal a quick and easy procedure with predictable result.

DEFINITION“The soft tissue along the junction of

the hard and soft palates on which pressure within the physiologic limit of the tissues can be applied by a denture to aid in the retention of the denture” -GPT

POST PALATALLL SEAL

PTERYGOMAXILLARY SEAL

Glossary

Border seal / Valve seal –The contact of the denture border with the underlying or adjacent tissues to prevent the passage of air or other substances.

Posterior palatal seal / post palatal seal –The seal at the posterior border of a maxillary removable dental prosthesis.

PTERYGOMAXILLARY SEAL -Pterygomaxillary seal extends through pterygomaxillary notch continuing for 3 to 4 mm anterolaterally approximating the mucogingival junction.

PTERYGOMAXILLARY NOTCH –The palpable notch formed by the junction of the maxilla and the pterygoid hamulus of the sphenoid bone.

FOVEA PALATINI – Two small pits or depressions in the posterior

aspect of the palatal mucosa one on each side of the midline, at or near the attachment of the soft palate to the hard palate.

HARD PALATE –

Bony portion of the roof of the mouth.

SOFT PALATE -The movable part of the palatal anatomy posterior to the hard palate.

VIBRATING LINE –An imaginary line across the posterior part of the palate marking the division between the movable and immovable tissues of the soft palate. This can be identified when the movable tissues are functioning

ANTERIOR VIBRATING LINE -The anterior vibrating line is an imaginary line at the junction of attached tissues overlying the hard palate and the movable tissues of the immediately adjacent soft palate.

POSTERIOR VIBRATING LINE –

The posterior vibrating line is an imaginary line at the junction of the aponeurosis of the tensor veli palatini muscle and the muscular portion of the soft palate

ANATOMY OF THE HARD PALATE

i) Palatal process of the maxillaii)Horizontal process of the palatine bone

i) Palatal process of the maxillaforms 3/4th of the hard palate.

ii) Horizontal plate of palatine boneForms posterior 1/4th of the hard palate.

Posterior nasal spine project out from horizontal plate.

Along the border, tensor veli palatini muscle is attached.

ANATOMY OF THE SOFT PALATESeparates oral and nasal parts of the pharynx.Anterior third of the soft palate contains little

muscles and palatine aponeurosisMuscle of the soft palate-

i) Tensor veli palatiniii) Levator veli palatini iii) Palatoglossusiv) Palatopharyngeusv) Muscularis uvulae

I) TENSOR VELI PALATINI

Origin – scaphoid fossa of the pterygoid process and

posteriorly from the medial aspect of the spine of the sphenoid bone.

Insertion – palatine aponeurosisNerve supply- nerve to medial pterygoidAction – tenses the soft palate and depress it by

flattening its arch.

II. LEVATOR VELI PALATINI

Origin – Inferior surface of the petrous part of temporal bone

Insertion – palatine aponeurosisNerve supply- cranial part of accessory

nerve via pharyngeal plexusAction – elevate the soft palate and pull it

slightly backwards

III.PALATOGLOSSUSOrigin – palatine aponeurosisInsertion – side of the tongueNerve supply – cranial part of accessory

nerve via pharyngeal plexusAction – elevates root of the tongue and

narrows oro-pharyngeal isthmus

IV.PALATOPHARYNGEUSOrigin – palatine aponeurosisInsertion – posterior boarder of thyroid cartilageNerve supply – pharyngeal plexusAction –pulls the pharynx up forward and

medially, thus shorten it during swallowing

V. MUSCULUS UVULAEOrigin – posterior nasal spine of palatine

bone and superior surface of palatine aponeurosis

Insertion –mucous membrane of uvulaNerve supply – pharyngeal plexusAction – elevates uvula

First four muscles are conjointly associated with mastication, swallowing and respiration.

Tensor veli palatini muscle should be displaced by the posterior border of the denture.

Boundaries of the posterior palatal seal areaAnteriorly – anterior vibrating linePosteriorly – posterior vibrating lineAnterolaterally extented ahead of hamular notchSuperoinferiorly – soft palatal tissues

Anatomy of the posterior palatal seal area

Anterior part of the soft palate contains palatine aponuerosis and is relatively less movable.

Most lateral part of the soft palate flows into the pterygomaxillary notch.

Pterygomaxillary notch is filled with the areolar tissue which is easily displaceable.

Posterior part soft palate slopes strongly downwards and is freely movable.

Functions Of Posterior Palatal Seal

In relation to the Special tray:To create slight displacement of the soft

tissues.To establish a positive contact posteriorly to

prevent the impression material from sliding into pharynx.

To serve a s a guide for positioning of impression tray,to some extent.

To determine, if the potential denture border has the required retention and seal.

In relation to a completed maxillary complete denture:

Retention is enhanced as the posterior palatal seal maintains the contact with the anterior portion of the soft palate during functional movements of the stomatognathic system i.e.

MasticationDeglutition Phonation

Close contact of the tissues with the denture base prevents food from getting under the denture.

Firm contact is provided with the soft tissues thus diminishing or eliminating gagging.

It supplies sunken distal borders which are less conspicuous to the dorsum of the tongue.

It supplies a thick border to counteract denture warpage i.e dimensional changes due to the laboratory procedure of methacrylate resin.

RATIONALE FOR POSTERIOR PALATAL SEAL

To create partial vacuum beneath the maxillary denture which is activated only when horizontal or lateral tipping forces are directed against the denture.

Determination of Anterior vibrating line

Valsalva maneuver ‘Ah’ in short vigorous burstsPalpation Swallowing methodUltrasound

Anterior vibrating line is not a straight line due to projection of posterior nasal spine.

Determination of posterior vibrating line‘Ah’ in normal unexaggerated fashion.PalpationUltrasound

Determination of the hamular notch

Palpation by means of i) T-burnisherii) Mouth mirror

Hamular notch should not be confused with the small depression present sometimes on the residual alveolar ridge.

Classification of the soft palateBased upon the angle that soft palate

makes with the hard palateClass I – Soft palate is rather horizontal as it extends posteriorly with minimal muscular activityClass III –Most acute contour in relation to the hard palate,marked elevation of musculature to create velopharyngeal closure.Class II – palatal contour lie between Class I and Class III

Types Of Posterior Palatal Seal Area

According To Shape:BEAD ON CAST:

Single bead at the distal margin of the denture.

DOUBLE BEADED:

One bead at the distal margin and other at anterior aspect of the palpated posterior palatal seal area.

SINGLE BEAD

DOUBLE BEAD

BUTTERFLY SHAPED:Deepest at the mostcompressible area of the posterior palatal seal area. Itmerges gradually with itsanterior and posteriorborders.

BUTTERFLY SHAPED

BUTTERFLY SHAPED WITHBEAD ON DISTAL EDGE OFDENTURE:Deepest part lies at the distal most part of posterior sealarea,in the form of bead.

BUTTERFLY SHAPED WITH WIDENED POSTERIOR PALATAL SEAL IN EACH HAMULAR NOTCH REGION:

More wide in each of the hamular notches.

Studies done by the workers shown that altering the type of posterior palatal seal affects the retention.None of the type is tested proved to be superior.

ACCORDING TO THE AREA COVERED

Posterior palatal seal can generally be extended to about 4 mm from the distal border of the denture. In hamular notch areas it may be narrow down to 2 mm.

Silverman advocates that denture can be extended to an average of 8.2 mm dorsally to the “flexion line”.

House modificationclass I: flat modified butterfly with the maximum antero-posterior width 3-4 mm

class II: high modified butterfly,2-3 mm with the maximum antero-posterior width 2-3 mm.

class III: intermediate a bead type- minimum width at posterior palatal spine.

Relationship of fovea palatini with posterior palatal seal area

Nagle and sears –fovea marks posterior limit of the hard palate.

Anderson and Storer – fovea lies in the glandular part of the soft palate,same view shared by Fenn

Silverman- seal can be extended 8.2 mm dorsally to vibrating line.

Skinner and Chung –experimentally shown the importance of the posterior palatal seal.

Lye – fovea are located 1.31 mm anterior to anterior vibrating line.

Fovea plotted against vibrating line, in his study.

1. Vibrating line was anterior to the fovea in 13.04 % cases.

2. Vibrating line and fovea coinciding in 17.39 % cases.

3. Vibrating line was posterior to fovea in 69.57% cases.

Chen – fovea are unreliable guides for locating the center portion of the posterior border of the maxillary denture.

however ,fovea should be used as guideline to the placement of the posterior palatal seal.

Techniques to record posterior palatal seal

Hardy and Kapur - classified the various techniques given in the literatures under

Conventional approach[Hardy and Kapur,1958]

Stage of recording –after an accurate and fully extended final impression has been made.

Method –1. Patient is seated in the upright position.2. Patient is asked to rinse with astringent

mouthwash.3. Palatal tissues are made damp-dry.4. Hamular notches located with T-burnisher and

marked with indelible pensile.

5. Posterior vibrating line located by asking patient to say “ah” in an unexaggerated fashion.

6. Anterior vibrating line marked by asking the patient to say “Ah” in short vigorous burst.

7. Markings are transferred to the cast from the tray which is held firmly to place, in the patients mouth.

8. Kingly scraper is used to score the cast. 9. Base plate is readapted to the conform scored

cast.

Advantages of placing the seal in the trial denture base

1. Trial base will be more retentive this can produce more accurate maxillomandibular records.

2. Retention of trial base gives physiologic security to the patient.

3. Practioner will be able to determine retentive qualities of dentures.

4. The new denture wearer will be able to realize the posterior extent of the denture which may ease the adjustment period.

Disadvantages of conventional approach

1. It is not physiologic technique.2. Potential for over compression of the

tissue is great.

Boucher’s Technique

Stage of recording: before Jaw relation

record:

Posterior vibrating line is located and transferred on the master cast

Temporary denture base is reduced to this line

‘V’ shaped groove is scraped 2mm anterior to the line

According to Boucher narrow bead like seal is more effective

Fluid Wax Technique

Stage of recording: after making the final impression

MethodFour type of waxes can be used Iowa wax (white) by E.S Smith Korecta wax (orange) by O.C Applegate H-L physiologic paste (yellow white) by C.S

Harkins Adoptol (green) by Nathan G Kaye

Head and tongue position are of importance

According to Nelson effective seal can be established with soft palate impressed in its most functionally depressed position

Head position 30 degree downward below the horizontal plane

Tongue- firmly held against mandibular tray handle

Molten wax is applied over the seal area

Press gently into place for 4-6 min.

Head is flex downward and rotated side to side

After 4-6 min impression tray is removed from the mouth and examine for tissue contact

Excess wax should be removed with hot scalpel

Advantages:

1. Physiologic technique.

2. Over compression is avoided.

3. More retentive trial base.

4. Mechanical scraping of cast is avoided.

Disadvantages:

1. Time consuming.

2. Difficulty in handling the material.

Technique using stick compound

1. Stages of recording: at the time of border molding

Method –

Instead of fluid wax, stick compound is used.

Apply the compound in between ant. and post. vibrating line and pressed gently into the patient mouth.

Tray is removed and checked for positive contact.

Extended palatal technique: (Silverman 1971)

Denture border is extended 8mm approximately beyond the anterior vibrating line.

Not widely used currently.

Method -1. After border molding tray is extended by

adding black compound.2. Green stick compound is added to the seal

area and record is made with head flexed 30 degree downward.

Arbitrary scraping of cast1. Least accurate method 2. Relies upon the dentist’s recollection of

the palatal configuration and tissue compressibility.

3. A V-shaped groove 1 to 1.5mm deep is carved into the cast at location of bead.

4. The bead will be 1 to 1.5mm high,1.5mm wide at base and sharp at its apex.

5. Depth is determined by thickness of the soft tissue

Trouble shooting Distal border of the denture may be 1. Overextended2. Under extended3. Under post dammed4. Over post dammed

Overextension The denture border extending onto active

portion of the soft palate. Symptoms1. Difficulty in swallowing2. Areas of redness or ulceration3. Sharp pain during function indicates

overextension over the pterygoid hamulus

Correction – correct marking of the posterior palatal seal area and denture border correction accordingly.

Under extension It is due to failure to record the proper

posterior extent of the seal area.

Correction (Yuuji Sato et al JPD 2000;83,3:371-3)

1. Adapt the baseplate wax to PPSA.

2. Soften the wax in a warm water bath.

3. Try-in the denture and adapt the wax lightly to obtain palatal seal.

4. Shape the surface of the wax.

5. Mix silicone putty and adapt it firmly to wax and palate.

6. Remove denture and silicone putty core from the mouth.

7. Remove the silicone putty and wax from the denture.

8. Roughen the post. border of denture and prepare the 45degree bevel joint on polish surface.

9. Apply adhesive on bevel.

10. Reposition the putty on the denture and add non-irritating direct relining resin.

11. Seat the denture in mouth and press the silicone putty lightly until the resin polymerized

12. Remove the denture from the mouth and remove silicone putty from the denture

13. Now finish and polish the denture.

Under postdamming

Can be detected by inserting wet denture base into the mouth.

Wet denture slowly pressed in the palatal region holding mirror in the posterior palatal region.

Escape of air bubble is noted.Escaping air bubbles indicates under extension.

correction – should be made accordingly.

Over postdamming

Moderate over postdamming- redness can be seen.

Severe postdamming – dentuer dispalce downwards.

Correction – reduce the overdammed areas.

Method for correcting PPS area of maxillary complete denture

(Frank Leuciello JPD 1979;42(6):690) Add the compound to establish adequate peripheral

seal.

Add mouth temperature wax over the compound to establish the seal.

Make a stone matrix.

Paint the separating medium to the stone matrix.

Remove the compound and the wax.

Denture is replaced on stone cast and held firmly .

After wax-up and dewaxing, pack heat cure resin and cure at 1380 F for 12 Hrs.

Trim the excess and polish the denture.

2. Visible light cure resin can also be used.

Adding posterior palatal seal to metal denture bases

Acrylic resin can be added by making holes or retentive loops for acrylic resin.

Vernie A Fernandes et al(2008) studied about the anterior and posterior vibrating line as two separate line of flexion .

The palpatory method produced a line slightly anterior to anterior vibratory line located by valsalva maneuver.

Kim Y, Michalakis KX, Hirayama H(2008) The purpose of this study was to evaluate

the dimensional accuracy of various denture relining methods and materials on the maxillary posterior palatal seal area.

A stainless steel cast was constructed from a maxillary edentulous cast.

Five relining methods and materials were evaluated during this study, in regards to posterior palatal seal distortion.

(I) laboratory conventional heat-polymerizing method

II) laboratory heat/pressure-polymerizing method

(III) laboratory autopolymerizing method (IV) chairside autopolymerizing method

(V) chairside light-polymerizing method

They concluded chairside autopolymerising method exhibited smaller gap recordings than the rest of the tested complete denture relining methods.

Conclusion

Placing the posterior palatal seal in the denture is dentist’s responsibility and not the technician’s obligation, hence thorough knowledge of the anatomy, function and movements of the tissues of this region is required and should be applied to enhance the retention and thereby stability.

references

Essentials Of Complete Denture Prosthodontics-Winkler- 2nd Ed.

Prosthodontic treatment for edentulous patients- Zarb Bolender- 12TH Ed

Syllabus for complete denture –Heartwell -4th Ed

Reliability of fovea palatine for determining posterior border of maxillary denture-JPD 1980;43:133-137

HARDLY Kapur- PPS –its rational & importance- JPD,1958-386-397

Kim Y, Michalakis KX, Hirayama H.-Effect of relining method on dimensional accuracy of posterior palatal seal. An in vitro study-J Prosthodont. 2008 Apr;17(3):211-8. Epub 2007 Jan 11

A study to determine whether the anterior and posterior vibrating lines can be distinguished as two separate lines of flexion by unbiased observers: a pilot study.Indian J Dent Res. 2008 Oct-Dec;19(4):335-9.

Ansari IH.-Establishing the posterior palatal seal during the final impression stage.-J Prosthet Dent. 1997 Sep;78(3):324-6.

THANK YOU.